Band n78 (3.5 GHz)
Understanding Band n78
Band n78 emerged as the global 5G consensus because it balances three competing requirements: bandwidth (up to 500 MHz available), propagation (manageable 1 to 3 km cell radius for macro deployment), and international harmonization (allocated for IMT in all three ITU regions). No other single band offers this combination. Low-band (600 to 900 MHz) has great coverage but limited bandwidth; mmWave (26/28/39 GHz) has enormous bandwidth but very limited range.
At 3.5 GHz, propagation is sufficient for urban and suburban macro cells but insufficient for rural coverage without excessive tower density. Operators therefore deploy n78 as their primary capacity layer in populated areas while relying on low-band (n28, n71, n20) for rural and deep indoor coverage. The TDD duplex mode enables channel reciprocity for massive MIMO beamforming, similar to Band 41. Typical NR frame structures allocate 70 to 80% of time slots to downlink (e.g., DDDSU or DDDDDDDSUU patterns) to match asymmetric traffic demand.
Band n78 Technical Parameters
Subset of: Band n77 (3300–4200 MHz)
NR Configuration:
SCS: 30 kHz | Max channel BW: 100 MHz
Peak DL (100 MHz, 64T64R, 256-QAM): ~2 Gbps
Path Loss (3GPP UMa model):
PL = 131.1 + 37.6 log(dkm) dB at 3.5 GHz
1 km: 131.1 dB | 2 km: 142.4 dB | 3 km: 149.0 dB
vs. n41 (2.5 GHz): +2.9 dB more loss
vs. n77 (3.7 GHz): −0.5 dB less loss
Global 3.5 GHz Allocation Status
| Country/Region | Allocated Range | Total BW | Operators |
|---|---|---|---|
| Europe (typical) | 3400-3800 MHz | 300-400 MHz | 3-4 per country |
| South Korea | 3420-3700 MHz | 280 MHz | SK, KT, LG U+ (3) |
| Japan | 3600-4100 MHz | 400 MHz | NTT, KDDI, SB, Rak (4) |
| China | 3400-3600 MHz | 200 MHz | CT, CU (2) |
| Australia | 3400-3700 MHz | 350 MHz | Telstra, Optus, TPG (3) |
Frequently Asked Questions
Why is 3.5 GHz the global 5G band?
3.5 GHz balances bandwidth (300 to 500 MHz available), propagation (1 to 3 km macro cells), and global harmonization (40+ countries). The GSMA identified n78 as the priority 5G band. In China, CT and CU use n78 (3400 to 3600 MHz); in South Korea, 280 MHz is split among three operators. No other band offers this combination of capacity and coverage.
What is the difference between Band n77 and n78?
n78 (3300 to 3800 MHz) is a subset of n77 (3300 to 4200 MHz). A device supporting n77 inherently supports n78 frequencies but not vice versa. Different countries use different portions: Europe 3400 to 3800 (n78), US 3700 to 3980 (n77 partially outside n78), Japan 3600 to 4100 (spans both). Manufacturers typically support both for global compatibility.
How much spectrum do operators hold at 3.5 GHz?
Typically 80 to 100 MHz per operator. Europe: 300 to 400 MHz total among 3 to 4 operators. South Korea: 280 MHz among 3. Japan: 400 MHz among 4 (100 MHz each). A 100 MHz n78 carrier with 64T64R massive MIMO delivers 1 to 2 Gbps peak per sector. Carrier aggregation with low-band provides coverage fallback.